Traditionally, telephones have required the use of two hands plus the necessity of visual attention to the dialing mechanism. One hand acquires the mouthpiece/receiver combination (the handset) and the other hand, with visual guidance, initiates and completes the dialing sequence.
With the advent of portable, cellular telephones, there remains significant visual demand to initiate and dial the telephone. This has become a very dangerous distraction to the user, especially when the user is driving an automobile. Passengers, pedestrians, other vehicles and many other physical obstacles are placed at increased risk.
As an example, taking one's eyes away from the road to view the dialing mechanism of a telephone at a minimum, represents a three to six second visual lapse in attention to safe-driving. It is unlikely that drivers who routinely use portable phones while in transit, will decelerate and pull off to the side of the road and come to a stop to safely utilize this communication device. Even when a driver is paying full visual attention to driving, at routine highway speeds, when the brakes are applied, the vehicle will travel approximately 500 feet before coming to a full stop. Local city driving is equally hazardous because although vehicle speed is slower, traffic is heavier, with the separation between vehicles being less than on the highway, and there is less time to react to visual distractions.
Telephone dialing time has progressively increased because more digits have to be activated to complete the desired dialing string. Local calls, formerly of a 7-digit string, have recently required inclusion of an area code, thereby lengthening to a 10-digit string. Long distance calls now require an 11-digit string, and overseas calls require a 13-15 digit string.
When routinely-called number are programmed in the telephone, abbreviated dialing numbers are substituted for the full string of dialing digits. The dialing-time may be somewhat shorter, but there still is a lapse in visual attention to driving.
The driver-user of a cellular telephone usually takes one hand off the driving wheel to access and manually manipulate the telephone. During this time interval their gaze is directed to visually access the dialing mechanism. When pre-programmed telephone numbers are not available, then the user encounters a longer time-interval in which to dial a string of digits during which their visual attention is directed to other than safe driving.
Some users prefer to manipulate the dialing sequence with the same hand that is holding the handset. In this instance, what usually happens is that it is the thumb which accesses each digit. The thumb is shorter and is relatively massive because of its two joints and has less motility than the fingers to sequentially activate the appropriate string of digits. Use of the thumb to dial is therefore cumbersome, visually demanding upon the user, and takes an extended time to execute the dialing string.
Another disadvantage in attempting to dial a telephone while driving is dysmetria. Dysmetria is the visual undershooting or overshooting of the exact position of visual fixation on the desired target (the dialing mechanism). In shifting visual gaze from road to a relatively small telephone dial, the eyes almost always cause an initial miss of the target and a secondary and sometimes a tertiary fixation is required to accurately focus on the dialing mechanism.
Further, the greater the angular difference between straight-ahead viewing of the road, and the location of the telephone, the greater will be the dysmetria effect. Usually cellular telephones are located significantly below the windshield with a large angular difference from straight-ahead viewing of 40 to 70 degrees. Each successive fixation of the eyes on the telephone expends more time and therefore increases the lapse of visual attention from the primary function of safely operating a motor vehicle.
Whether the telephone that is utilized during driving is hands-free, or hand-held, it is important not to have to look at the dialing mechanism. It is also important to shape the telephone and position the various controls so that the device can be grasped and held in a prehensile manner. A prehensile manner allows the controls of a telephone to be activated in a naturally-grasping motion where the thumb is moving toward the fingers. This affords greater tactile familiarity with the tool and thereby lessens the visual demand to be looking at the telephone.